1. Field of the Invention
The present invention relates to an apparatus and a process for bonding dry metallic powder to a substrate and more particularly to impact extruding particles to form a continuous thin film on a metallic surface.
The use of impact or peen bond coating techniques has been limited in scope and to laboratory environments as a result of the failure to implement tribology in a practical apparatus for field use. Other bonding methods, such as binders or adhesive merely hold together a mass of discontinuous particles on a given surface. Pressures required for extrusion of the coating material into a continuous coat can destroy the bond between the coating material and the surface of the substrate.
2. Description of the Prior Art
The most pertinent prior patent is believed to be U.S. Pat. No. 3,758,976. This patent discloses a nozzle for blasting a powdered metal mixed with a media against a surface to be coated but does not disclose requirements for utilizing the process in commercial applications. U.S. Pat. No. 4,552,784 utilizes substantially the same steps as the above patent but substitutes rapidly solidified metals to form the powder mix.
Other prior patents include:
U.S. Pat. No. 4,312,900 disclosing a method of treating sliding metal contact surfaces which pits the workpiece surface to be coated, buffs a solid lubricant into the pits and reblasts to partially cover the pits followed by power buffing the surface.
U.S. Pat. No. 3,574,658 disclosing a method of producing a dry-lubricated surface which coats a glass bead media with lubricant for blasting the workpiece surface leaving the lubricant bonded to the surface being coated. Since the beads break down during the process the entire mix must be discarded after one use.
Exploitation of these patents has not been generally achieved on a commercial basis possibly for the reason problems to be overcome in utilizing the process commercially was not set forth, particularly for the peening type methods or for the reason many coating materials disclosed do not require a peening effect since they may be blasted on and leave a coating smear on a substrate.
This invention is distinctive over these patents by providing a virgin surface on a substrate by removing all contaminants and microscopic burrs and maintaining a desired coating/media ratio combined with atmospheric control when impingement burnishing to bond particles on and form a continuous film on a substrate surface. The peen plating process of this invention produces a unique effect not disclosed in these patents in which the peening not only forms a plating function but also a burnishing operation promoting parallel crystal orientation of the solid lubricant employed. Without such parallel orientation, the coating is more subject to corrosion and a shorter wear life by rapidly wearing which also results in a higher coefficient of sliding friction.